This project includes the investigation of molecular aspects of rabies virus infection in cell cultures, characterization of the pathogenesis and the immune response associated with rabies infection in experimental mammals, and improved methods for vaccination of man. The primary objective of molecular biological studies is the identification of rabies structural genes, and the cloning of the glycoprotein gene for the expression of viral-specific antigen in bacteria as an alternate source of rabies vaccine. Comparative studies with monoclonal antibodies against virion structural proteins of fixed and street rabies virus strains and rabies-related viruses show specificities as determined by (1) radioimmunoassay, (2) indirect immunofluorescence, (3) virus neutralization, (4) immunoprecipitation, and (5) in vivo protection in mice. Attenuated virus variants that have required their virulence for adult mice by serial cultivation in suckling mouse brain or in neuroblastoma cells appear to represent a selection of randomly produced revertant viruses. Chronic rabies virus infections have been examined extensively for (1) virulence phenotype of released virus, (2) cyclic variation in the percent of infected cells, (3) cyclic production of DI particles as well as occasional standard size virions of low infectivity, (4) induction of tumors in mice, and (5) virus-curing of cell cultures. In preliminary metabolic studies of rabies virus-infected cells, changes in physical size of cells and metabolic activity have been observed between infected, "cured" and non-infected control cells. Further attempts were made to characterize the cellular immune mechanisms in recovery from experimental rabies by adoptive intravenous transfer of lymphoid cells from immune donors to cyclophosphamide-treated rabies virus-infected recipients.